1. Field of the Invention
The present invention relates to silver halide photographic emulsions. In more detail, the present invention relates to fine-grain photographic silver halide emulsions of which an electron sensitivity has been remarkably increased by use of specific sensitizing dyes.
2. Description of the Prior Art
It has been well known to expand the light sensitive wavelength of silver halide emulsions by adding a certain kind of sensitizing dye in the art of preparation of the silver halide photographic emulsions.
It has also been previously found that the sensitive wavelength range of the emulsions of finely divided particles having a particle size of 0.2 microns not only is expanded when spectrally sensitized with using a certain kind of dye but also the light sensitivity of an intrinsic absorption range of the silver halide is expanded as disclosed in Japanese Patent Application No. 44-38248 U.S. Patent Application Ser. No. 38,485, filed May 18, 1970.)
On the other hand, it is required to reduce the grain size of the silver halide as small as possible in order to obtain high quality images in sensitive materials for high resolution recording and especially in sensitive materials for recording electron rays. Further, it is necessary to use emulsions having an electron sensitivity as high as possible in order to reduce electric charges on the surface of the sensitive material and to draw distinct images by reducing the amount of the electron rays so as to increase the speed of the electron ray recording.
One prior art technique for recording electron rays, for example, using the emulsions disclosed in U.S. Pat. Nos. 2,912,329; 3,173,791, and 3,264,110 and British Pat. No. 980,234, has the disadvantage that the electron ray must be converted to the visible ray corresponding to the intrinsic sensitivity of the gelatino silver halide photographic emulsion used for recordation using an intensifying screen.